[Merge M-53] Credit card editor for PaymentRequest UI.

chrome/android/java/res/layout/payment_request_editor_dropdown.xml

 <?xml version="1.0" encoding="utf-8"?>
 <!-- Copyright 2016 The Chromium Authors. All rights reserved.
      Use of this source code is governed by a BSD-style license that can be
      found in the LICENSE file. -->
 
 <LinearLayout
         xmlns:android="http://schemas.android.com/apk/res/android"
         android:layout_width="match_parent"
         android:layout_height="wrap_content"
-        android:orientation="vertical"
-        android:paddingBottom="@dimen/pref_autofill_content_spacing"
-        android:paddingStart="@dimen/pref_autofill_field_horizontal_padding"
-        android:paddingEnd="@dimen/pref_autofill_field_horizontal_padding">
+        android:layout_marginBottom="@dimen/pref_autofill_content_spacing"
+        android:layout_marginStart="@dimen/pref_autofill_field_horizontal_padding"
+        android:layout_marginEnd="@dimen/pref_autofill_field_horizontal_padding"
+        android:orientation="vertical">
 
     <TextView
             android:id="@+id/spinner_label"
             android:layout_width="match_parent"
             android:layout_height="wrap_content"
             android:textAppearance="@style/PreferenceFloatLabelTextAppearance" />
 
     <android.support.v7.widget.AppCompatSpinner
             android:id="@+id/spinner"
             android:layout_width="fill_parent"
             android:layout_height="wrap_content"
             android:layout_marginTop="@dimen/pref_autofill_field_top_margin" />
 
     <View style="@style/PreferenceSpinnerUnderlineView" />
 
 </LinearLayout>